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Distribution of ace-1R and resistance to carbamates and organophosphates in Anopheles gambiae s.s. populations from Côte d'Ivoire.

Ahoua Alou LP, Koffi AA, Adja MA, Tia E, Kouassi PK, Koné M, Chandre F - Malar. J. (2010)

Bottom Line: The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%.This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested.The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut Pierre Richet, BP 47 Abidjan, Côte d'Ivoire.

ABSTRACT

Background: The spread of pyrethroid resistance in Anopheles gambiae s.s. is a critical issue for malaria vector control based on the use of insecticide-treated nets. Carbamates and organophosphates insecticides are regarded as alternatives or supplements to pyrethroids used in nets treatment. It is, therefore, essential to investigate on the susceptibility of pyrethroid resistant populations of An. gambiae s.s. to these alternative products.

Methods: In September 2004, a cross sectional survey was conducted in six localities in Côte d'Ivoire: Toumbokro, Yamoussoukro, Toumodi in the Southern Guinea savannah, Tiassalé in semi-deciduous forest, then Nieky and Abidjan in evergreen forest area. An. gambiae populations from these localities were previously reported to be highly resistant to pyrethroids insecticides. Anopheline larvae were collected from the field and reared to adults. Resistance/susceptibility to carbamates (0.4% carbosulfan, 0.1% propoxur) and organophosphates (0.4% chlorpyrifos-methyl, 1% fenitrothion) was assessed using WHO bioassay test kits for adult mosquitoes. Then, PCR assays were run to determine the molecular forms (M) and (S), as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to G119S mutation.

Results: Bioassays showed carbamates (carbosulfan and propoxur) resistance in all tested populations of An. gambiae s.s. In addition, two out of the six tested populations (Toumodi and Tiassalé) were also resistant to organophosphates (mortality rates ranged from 29.5% to 93.3%). The M-form was predominant in tested samples (91.8%). M and S molecular forms were sympatric at two localities but no M/S hybrids were detected. The highest proportion of S-form (7.9% of An. gambiae identified) was in sample from Toumbokro, in the southern Guinea savannah. The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%.

Conclusion: This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested. The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.

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Map of Côte d'Ivoire showing the localities in the different ecological zones where anopheline mosquitoes were collected
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Figure 1: Map of Côte d'Ivoire showing the localities in the different ecological zones where anopheline mosquitoes were collected

Mentions: The study sites form a north-to-south transect across the Southern Guinea savannah, the semi-deciduous forest and the evergreen forest areas in Côte d'Ivoire. The last two zones are characterized by intensive human activities and agricultural land-degraded forest mosaic. Mosquitoes were collected during the rainy season from six localities: Toumbokro (7°N; 5°35' W), Yamoussoukro (6°82' N; 5°28' W) and Toumodi (6°55' N; 5°03' W) located in the Southern Guinea savannah, Tiassalé (5°88' N; 4°38' W) in a semi-deciduous forest area, then Nieky (5°20'N; 4°10'W) and Abidjan (5°33'N; 4°03' W) in a evergreen forest area (Figure 1). Samples were collected from coffee and cocoa industrial plantations in Toumbokro, banana cultivation fields in Nieky and in urban areas in Yamoussoukro, Toumodi, Tiassalé and Abidjan. Mosquitoes were collected at larval stage, brought to the laboratory and reared until for emergence of adults. A reference laboratory strain of An. gambiae s.s. named "Kisumu", native from Kenya and susceptible to all insecticides was used as control.


Distribution of ace-1R and resistance to carbamates and organophosphates in Anopheles gambiae s.s. populations from Côte d'Ivoire.

Ahoua Alou LP, Koffi AA, Adja MA, Tia E, Kouassi PK, Koné M, Chandre F - Malar. J. (2010)

Map of Côte d'Ivoire showing the localities in the different ecological zones where anopheline mosquitoes were collected
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908637&req=5

Figure 1: Map of Côte d'Ivoire showing the localities in the different ecological zones where anopheline mosquitoes were collected
Mentions: The study sites form a north-to-south transect across the Southern Guinea savannah, the semi-deciduous forest and the evergreen forest areas in Côte d'Ivoire. The last two zones are characterized by intensive human activities and agricultural land-degraded forest mosaic. Mosquitoes were collected during the rainy season from six localities: Toumbokro (7°N; 5°35' W), Yamoussoukro (6°82' N; 5°28' W) and Toumodi (6°55' N; 5°03' W) located in the Southern Guinea savannah, Tiassalé (5°88' N; 4°38' W) in a semi-deciduous forest area, then Nieky (5°20'N; 4°10'W) and Abidjan (5°33'N; 4°03' W) in a evergreen forest area (Figure 1). Samples were collected from coffee and cocoa industrial plantations in Toumbokro, banana cultivation fields in Nieky and in urban areas in Yamoussoukro, Toumodi, Tiassalé and Abidjan. Mosquitoes were collected at larval stage, brought to the laboratory and reared until for emergence of adults. A reference laboratory strain of An. gambiae s.s. named "Kisumu", native from Kenya and susceptible to all insecticides was used as control.

Bottom Line: The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%.This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested.The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut Pierre Richet, BP 47 Abidjan, Côte d'Ivoire.

ABSTRACT

Background: The spread of pyrethroid resistance in Anopheles gambiae s.s. is a critical issue for malaria vector control based on the use of insecticide-treated nets. Carbamates and organophosphates insecticides are regarded as alternatives or supplements to pyrethroids used in nets treatment. It is, therefore, essential to investigate on the susceptibility of pyrethroid resistant populations of An. gambiae s.s. to these alternative products.

Methods: In September 2004, a cross sectional survey was conducted in six localities in Côte d'Ivoire: Toumbokro, Yamoussoukro, Toumodi in the Southern Guinea savannah, Tiassalé in semi-deciduous forest, then Nieky and Abidjan in evergreen forest area. An. gambiae populations from these localities were previously reported to be highly resistant to pyrethroids insecticides. Anopheline larvae were collected from the field and reared to adults. Resistance/susceptibility to carbamates (0.4% carbosulfan, 0.1% propoxur) and organophosphates (0.4% chlorpyrifos-methyl, 1% fenitrothion) was assessed using WHO bioassay test kits for adult mosquitoes. Then, PCR assays were run to determine the molecular forms (M) and (S), as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to G119S mutation.

Results: Bioassays showed carbamates (carbosulfan and propoxur) resistance in all tested populations of An. gambiae s.s. In addition, two out of the six tested populations (Toumodi and Tiassalé) were also resistant to organophosphates (mortality rates ranged from 29.5% to 93.3%). The M-form was predominant in tested samples (91.8%). M and S molecular forms were sympatric at two localities but no M/S hybrids were detected. The highest proportion of S-form (7.9% of An. gambiae identified) was in sample from Toumbokro, in the southern Guinea savannah. The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%.

Conclusion: This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested. The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.

Show MeSH
Related in: MedlinePlus